The purpose of the proposed study is to examine whether the formation of new synapses after deprivation of one input to a target area in the central nervous system can be accelerated by chronic microstimulation of a remaining input. Cats will be used for the experiments. Lesions will be made at the nucl. ventralis lateralis of the thalamus to deprive the input to the motor cortex. Area 2 of the sensory cortex is known to send association fibers to the motor cortex. Whether this input is reinforced by the deprivation of the input from the n. vent. lat. will be examined first in the control experiments. This will be done by measuring the change of the rise time of EPSPs in the motor cortex neurons elicited by stimulation of area 2 and also by examining the terminal sites of new synapses of area 2 fibers on motor cortical neurons using an electron microscope. After obtaining the control parameters, area 2 will be stimulated chronically during the course of the recovery after the lesion in the n.vent. lat. Then the rise time of the EPSPs and the sites of the new synapses will be compared with those in the control animals. It is expected that the microstimulation may provide a competitive advantage to area 2 neurons in the synaptic formation among the various inputs to the motor cortex. If this is the case, then the results will provide a basis for developing a new surgical method for the alleviation of symptoms resulting from the damage of a part of the central nervous system by reinforcing a selective input to the target area to compensate the lost function.